I been having same issue as many ppl it would appear, so i started a thread for the fix rather then add to all previous threads. Anyways i've gotten the DFSVC.exe error as well as errors trying to reinstall WoWAceUpdater. The fix appears to be to do a repair of Microsoft .NET 2.0 Runtime.
The Redistibutable can be found at http://www.microsoft.com/downloads/details.aspx?familyid=0856EACB-4362-4B0D-8EDD-AAB15C5E04F5&displaylang=en for 32bit operating systems.
Or at http://www.microsoft.com/downloads/details.aspx?familyid=B44A0000-ACF8-4FA1-AFFB-40E78D788B00&displaylang=en for 64bit operating systems.
Simply run the program and choose 'Repair' then restart after it finishs and you should be up and running again.